A color electrophotographic printer can print both color and monochrome (commonly referred to as "black and white") images on sheets of paper or other media The printer has color and monochrome heads positioned adjacent each other, and uses the color heads to print the color sheets and the monochrome head to print the monochrome sheets. The paper feed path of the printer has two positions in which images may be printed on sheets of media with the color and monochrome heads: a color position, in which sheets feed past both the color and monochrome heads and can print both color and monochrome images, and a second, monochrome position, in which the sheets feed past only the monochrome head and can print only monochrome images. The printer can operate in a high speed mode, with a high printing speed, or in a high yield mode, with a slower printing speed but longer supply use.
While the high speed mode of the printer has the highest printing speed, certain sacrifices must be made in order to obtain such speed. In particular, the paper feed path must remain in the color position, in which the sheets feed past both the color and the monochrome printing heads. However, the color printing heads receive unnecessary wear in this position when only monochrome sheets are printed, as they are not used, but nevertheless contact the sheets that are printed. The color printing heads wear out and fail much more frequently than would otherwise occur if only the monochrome printing head was in contact with the sheets printed in monochrome, and must consequently be replaced at considerable expense and inconvenience.
From a wear and reliability standpoint, it is preferable to utilize the high yield mode. The paper feed path changes between the two positions, so that the color printing heads only contact the sheets when a color image is printed, but not when a monochrome image is printed, thus minimizing wear. However, as noted, this mode results in relatively slow printing speeds, as considerable time is required for the position of the paper feed path to change back and forth.
It would thus be advantageous to increase the printing speed of the printer by printing some monochrome images with the paper feed path in the color position, where it prints both color and monochrome images, without changing the paper feed path to the monochrome position and slowing down the printing speed, but not such a large number that would result in excessive wear to the color printing heads.